Tropical Fish Hobbyist

spot some critters on the live rock that don’t come out during the day, I caught a glimpse of a crab hiding in a hole in one of the rocks near the bottom of the pile. It appeared to be about an inch wide and was dark green to black in color. Its legs were short and squatty. I only saw it for a moment and didn’t have time to photograph it. Any idea what

With a photo, identifying hitchhiking crabs with any level of certainty can be very difficult, but without

type of crab it is, and will it harm my corals or snails?

Nathan Pesin via email

A

The nutritional value of the popular phytoplankton products were recently tested by 2 feeding trials on juvenile hard clams, Mercenaria mercenaria. The results were published in the November/December 2006 issue of the peer review journal Zoo Biology.

The products tested included; both powdered and liquid products stored at room temperature, the popular frozen concentrate, DT’s® Live Marine Phytoplankton, A product marketed as being a refrigerated live phytoplankton but with more species than DT’s, and a product by the same company that is advertised as having the same

nutritional profile as live phytoplankton.

several ti

Toughest Clown
Which clownfish do you
think is the hardiest? I’ve tried
to keep ocellaris clownfish
mes but haven’t had any luck
keeping them alive.

Pat Stover

Kingston, Rhode Island

a photo, I wouldn’t even hazard a guess as to the identity of the crab you saw. However, if I were you, I would try to trap and remove this mystery crab, as most true crabs will eventually become problematic in reef systems, opportunistically munching on desired fauna, such as coral polyps and snails.

To catch the crab, you can try moving the rock it hides in to a separate container, waiting for the crab to emerge at night, and then moving the rock—sans crab—back to your reef system. But since, as you mention, the rock you saw the crab in is located toward the bottom of the pile, you might have better luck using a baited trap. Position a glass against the rock it hides in and place some meaty bait in the bottom of the glass. Sometime after lights out, the crab should enter the glass to get the bait, but the smooth sides of the glass will prevent it from climbing back out.

Then all you have to do is remove the glass, crab and all, the following morning. You might catch a few desirable critters in the process, but you’ll eventually get your quarry.

Q

“The commercial blend,

DT's® Live Marine Phytoplankton seems to represent a good substitute to lab grown algae for clams held in ornamental or experimental aquariums.”

Wiley-Liss, Inc.

Results

DT’s® Live Marine Phytoplankton was the only product tested that was effective in growing juvenile clams.

The results from all of the other products tested were consistent with not feeding the clams at all.

Amphiprio

I must admit to being more than a bit surprised that you’ve had such a hard time keeping ocellaris clownfish n ocellaris alive as, in my humble opinion, this species is fairly durable and even well-suited for beginners. If you try this species again, you can improve your odds of success by choosing tank-raised specimens, which are commonly available (albeit usually more expensive than wild-caught specimens) in the trade.

Getting to your question, the tomato clownfish Amphiprion frenatus is among the most durable of the clownfishes. It’s also one of the bigger species, reaching a respectable 5½ inches in length at maturity. You should also be able to get captive-raised specimens of A. frenatus, which are even more “bulletproof.” D